1. Field of the Invention
The present invention relates to disk drives. More particularly, the present invention relates to a head stack load comb for use in the assembly of a disk drive and a method of assembling a disk drive utilizing the head stack load comb, in which the head stack load comb provides for controlled head loading.
2. Description of the Prior Art and Related Information
A huge market exists for hard disk drives for mass-market host computer systems such as servers, desktop computers, and laptop computers. To be competitive in this market, a hard disk drive should be relatively inexpensive, and should accordingly embody a design that is adapted for low-cost mass production. Further, there exists substantial competitive pressure to continually develop hard disk drives that have increasingly higher storage capacity, that provide for faster access to data, and at the same time conform to decreasingly smaller exterior sizes and shapes often referred to as “form factors.”
Satisfying these competing constraints of low-cost, small size, high capacity, and rapid access requires innovation in each of numerous components and methods of assembly including methods of assembly of various components into certain subassemblies. Typically, the main assemblies of a hard disk drive are a head disk assembly and a printed circuit board assembly.
The head disk assembly includes an enclosure including a base and a cover, at least one disk having at least one recording surface, a spindle motor for causing each disk to rotate, and an actuator arrangement. The printed circuit board assembly includes circuitry for processing signals and controlling operations.
Actuator arrangements can be characterized as either linear or rotary; substantially every contemporary cost-competitive small form factor drive employs a rotary actuator arrangement.
The rotary actuator arrangement is a collection of elements of the head disk assembly; the collection typically includes certain prefabricated subassemblies and certain components that are incorporated into the head disk assembly. The prefabricated assemblies include a pivot bearing cartridge and, in some cases, a prefabricated head stack assembly which may include the pivot bearing cartridge. Other components of the rotary actuator arrangement are permanent magnets and an arrangement for supporting the magnets to produce a magnetic field for a voice coil motor. The prefabricated head stack assembly includes a coil forming another part of the voice coil motor. The prefabricated head stack assembly also includes an actuator body having a bore through it, and a plurality of arms projecting parallel to each other and perpendicular to the axis of the bore. The prefabricated head stack assembly also includes head gimbal assemblies that are supported by the arms. Each head gimbal assembly includes a load beam and a head supported by the load beam.
In the course of making a head disk assembly, the heads of the head stack assembly (HSA) are merged with the disks during an operation known as a “head-disk merge operation.” As previously discussed, a head disk assembly often includes a base, a spindle motor, and plurality of disks mounted on the spindle motor. During the head-disk merge operation, a corresponding set of heads of the HSA is positioned proximate to the outside diameters of the disks utilizing a load comb. The load comb is used to separate the heads of the HSA. The load combs are typically ramped and the HSA is rotated such that lift tabs of the arms of the HSA slide down the ramped load comb until each head is rotated onto the disk such that the heads are “merged” with the disks. After the heads are merged with the disks, the load comb is removed.
Typically, in this arrangement, the load comb is made out of stainless steel. The slope of the ramps of the load comb is designed to load each head onto each disk with a low occurrence rate of head disk interactions. Head disk interactions, such as head slaps, may increase the risk of head and disk damage. Unfortunately, head disk interactions, such as head slaps, still occur and with time, and after many uses, the slope of the ramps of the load comb may change such that they may fail to adequately control the load velocity of the heads onto the disks properly. This failure to control the load velocity may lead to an increased rate of head slaps when heads of the HSA are merged onto disks. In addition, current ramps of load combs create a certain amount of lateral motion between the head and the disk when the head is merged to the disk, which increases the risk of head and disk damage due to head disk interactions.